Pintle pump

ABSTRACT

The invention comprises a radial piston hydraulic pump or motor having a control to position the cylinder barrel on a tapered pintle to maintain the necessary flow of leakage fluid in each direction outwardly between their bearing surfaces for different or varying operating conditions. The control includes a servomotor to urge the cylinder barrel on the taper of the pintle in accordance with the flow of the leakage fluid discharged at one end of the pintle with such flow regulated so as to equal or exceed the flow of leakage fluid discharged at the other end of the pintle.

United States Patent [191 Douglas July 10, 1973 PINTLE PUMP 2, 53,153;3/132; gishgipngl. ..39l/485 [75] Inventor: James K g Shorewood, wis- 3,us et 08/122 [73] Assignee: The Oilgear Company, Milwaukee, PrimaryExaminer-William L. Freeh Wis. AttorneyT. Lloyd LaFave {22] Filed: May30, 1972 [57] ABSTRACT PP 258,121 The invention comprises a radialpiston hydraulic pump or motor having a control to position the cylinder52 [1.8. CI. 91/484, 91/492 barrel on a tapered pintle maintain thenecessary 51 1111. c1. F0lb 13/06 flow of leakage fluid in directionoutwardly [58] Field 01 Search 91/484, 492, 485, tween theirbearingsurfacesfor different Orvarying P- 91/489 erating conditions. Thecontrol includes a servomotor to urge the cylinder barrel on the taperof the pintle in [56] References Cited accordance with the flow of theleakage fluid dis- UNn-ED STATES PATENTS charged at one end of thepintle with such flow regulated so as to equal or exceed the flow ofleakage fluid 5322; discharged at the other end of the pintle. 2:449:29;9/1948 Hoffer 308/9 5 Claims, 1 Drawing Figure 24 33 I /0 57 2 3 62 /6 Il I 3? 5a PINTLE PUMP BACKGROUND OF THE INVENTION The invention pertainsto a radial piston hydrostatic machine operable as a pump or as a motorand having a tapered pintle for valving motive fluid to the cylinders ofa cylinder barrel journalled on the pintle. And more particularly itpertains to such a machine having a control to move the cylinder barrelon or off the taper of the pintle to adjust the running clearancebetween their mating tapered bearing surfaces in accordance withoperating pressure and the flow of leakage fluid escaping at each end ofthe pintle.

This type of tapered pintle hydraulic pump or motor is shown anddescribed in US. Pat. No. 2,231,361 issued Feb. 11, 1941. It shows anend cylinder arranged on the end of the cylinder barrel, a piston fittedin the end cylinder and secured to the driveshaft for coupling thecylinder barrel and drive shaft for rotation with each other. Leakagefluid escaping from between the tapered bearing surfaces of the cylinderbarrel and pintle at thpe small end of the pintle enters the endcylinder and is discharged therefrom through a flow restricting passage.The pressure of the leakage fluid in the end cylinder urges the cylinderbarrel toward the large end of the pintle. The machine is also providedwith built in stops to limit the movement of the cylinder barrel ineither direction and a prressure relief valve connected to a dischargepassage for the leakage fluid to limit the pressure of leakage fluid inthe end cylinder to a preset maximum value.

The prior art control of the running clearance between a cylinder barreland a tapered pintle is responsive to the flow of leakage fluid at oneend of the pintle independent of the flow of leakage at the other end ofthe pintle.

Although the tapered surfaces are machined to provide mating surfaces,machining tolerances leave some error which may be compensated in partby select fitting of pintle and cylinder barrel parts in order toprovide at least as much leakage flow under normal operating condtionsat the large end of the pintle as at the small end of the pintle.However this does not give positive protection against operatingconditions that may cause the leakage flow along the bearing surfaces atthe large end of the pintle to decrease below a minimum value necessaryto lubricate and cool such bearing surfaces and prevent seizuretherebetween.

The leakage flow at the large end of the pintle may decrease relative tothe leakage flow at the small end of the pintle, for example, when'thereis a change in oil temperature causing uneven expansion of pintle and orcylinder barrel.

SUMMARY OF THE INVENTION The invention provides a radial pistonhydraulic pump or motor having a cylinder journalled on a tapered pintleand axially adjustably positioned on the pintle to vary the runningclearance between their bearing surfaces to maintain a prescribedminimum flow of leakage fluid therebetween and escaping at each end ofthe bearing surfaces sufficient to cool and lubricate the bearingsurfaces.

The cylinder barrel is urged in a direction off of the taper of thepintle by bias forces consisting of a spring and the pressure of theleakage fluid flowing between the tapered bearing surfaces. The cylinderbarrel is urged in a direction on the taper of the pintle by thepressure of leakage fluid received in a cylinder arranged at one end ofthe cylinder barrel and pintle and discharged therefrom through avariable orifice or through a fixed orifice in parallel with a variableopenmg.

Leakage fluid flows outwardly in both directions from a port locatedintermediate the ends of the pintle and the end cylinder receives suchflow from the small end of the pintle. Flow of leakage fluid along thebearing surface-of the large end of the pintle is conducted to dischargethrough a fixed orifice. The rate of flow of leakage fluid from each endof the bearing surfaces and discharging through their respectiveorifices each develop a pressure which are substantially equal when theleakage flows from each end of the pintle bearing surface are equal. Thepressures at these orifices are applied in opposition on a valve memberof a servovalve controlling the opening of the variable orifice, anopening in parallel with the fixed orifice. When a difference in thepressures at the orifices exists due to the pressure of leakage fluidfrom the large end of the pintle being less than that from the small endof the pintle, the valve member is displaced by the resulting differencein pressures to increase the opening for the discharge of leakage fluidfrom the small end of the pintle and thus reduce its pressure until theopposing pressures of leakage fluids are equal. This reduces thepressure in the end cylinder so that the cylinder barrel moves off ofthe taper to increase the running clearance and increase the leakageflows until the servovalve can equalize its opposing pressures.

Thus, the present invention provides a control for positioning thecylinder barrel on thee tapered pintle in accordance with the lessereffective running clearance occurring at either end portions of theirbearing surfaces and as may exist or occur during varying operatingconditions. Such positive protection assures not less than a prescribedminimum effective running clearance for each end portion of the bearingsurfaces and permits the selection of a lower minimum running clearancethat will nevertheless permit sufficient flow of leakage fluid forlubricating and cooling of the bearing surfaces at the most severeoperating conditions.

A pump, for example, embodying the present invention and having anoutput capacity equivalent to 500 horsepower, is designed at ratedoutput to provide a flow of leakage fluid between the bearing surfacesof the pintle and cylinder barrel on the order of 2 percent of pumpoutput. The pump is also designed to have a maximum running clearance of0.007 inch, as at startup, and a minimum running clearance of 0.001inch, as at maximum pressure and temperature.

It is therefore an object of the invention to control the position of acylinder barrel on a tapered pintle to maintain a necessary minimum flowof leakage fluid betweeen both end portions of their bearing surfaces.

Another object of the invention is to control the position of a cylinderbarrel on a tapered pintle to maintain an effective minimum runningclearance between both end portions of the bearing surfaces of thepintle and cylinder barrel.

Another object of the invention is to urge a cylinder barrel on atapered pintle by a control cylinder responsive to the pressure ofleakage fluid escaping from the small end of their bearing surfaces toeffectively override such control in response to a relative decrease inpressure of leakage fluid escaping from the large end of the bearingsurfaces.

Another object of the invention is to make cylinder barrel and pintleparts for pumps interchangeable without the necessity for select fittingby providing a control that maintains an effective minimum runningclearance between both end portions of said parts to compensate formachining tolerances for all operating conditions of the pumps.

Other objects and advantages of the invention will be apparent from thefollowing description and accompanying drawing, in which:

FIG. 1 is a longitudinal view, with part broken away and part incross-section of a pump illustrating an embodiment of the presentinvention.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION A variable displacementhydraulic machine, FIG. 1, is operable as a pump or as a motor, and forconvenience is herein referred to as a pump. The pump comprises a closedcasing 1, having a removable head 2 attached to its front end and a hub3 formed integral with the casing at its rear end. A slideblock 4 issupported in a known manner for transverse horizontal movement in thecasing. A hollow thrust member 6 is rotatably supported in theslideblock by thrust bearings 7, 8. The eccentricity of the axis of thethrust member 6 with respect to the axis of the cylinder barrel 20 isdetermined by the position of the slideblock 4. Such eccentricitydetermines the displacement of the pump.

A stationary valve shaft or pintle 9 has a rear part rigidly secured inthe hub 3 of the casing, and the front part 10 of the pintle is arrangedwithin the thrust member. The pintle 9 is provided wiith an uppersegmental port 11 and a lower segmental port 12, which communicaterespectively with upper and lower passages 13, 14 respectively formedlongitudinally in the pintle. The rear end of these passages extendradially outward .through the rear part of the pintle to inlet andoutlet ports 16, 17 for connection to an external circuit. Th forwardpart 10 of the pintle, within the thrust member, is tapered to a reduceddiameter and supports the cylinder barrel 20, which has a bushing 21press fitted therein and accurately fitted upon the forward tapered part10 of the pintle so that the cylinder barrel is freely rotatable aboutthe pintle.

The cylinder barrel 20 is provided with a plurality of radial cylinders22 which are arranged in circumferential rows, and in longitudinal rows.The cylinder barrel 20 is provided with a plurality of passages 23 eachof which communicates with at least one cylinder in each of thecircumferential rows. Each such passage communicates with a cylinderport 24 formed in the bushing which, in turn, communicates with thepintle ports ll, 12, alternately, as the cylinder barrel rotates.

A piston 25 is fitted in each cylinder 22 and prrovided with a contactface upon its outer end. The contact face of each piston engages withthe reaction surface formed on a thrust ring 26, fixed within thrustmember 6.

Cylinder barrel 20 is connected to a driveshaft 27 so that it may rotatetherewith. The driveshat't is rotatably supported by thrust bearingsarranged in the end head 2 and by a thrust bearing 29 arranged in arecess formed in the forward end of the pintle.

As shown, the cylinder barrel 20 has its body or main portion extendedbeyond the small end of the pintle to form and end cylinder 32. This endcylinder has arranged therein a piston 33 which is splined upon theshaft and a shoulder formed thereon limits outward movement of thecylinder barrel. The piston 33 closes the end cylinder and also servesas a driver coupling the cylinder barrel to the shaft 27 for rotationtogether. A piston ring is fitted in the radially outer part of thepiston 33 to prevent liquid from escaping through the outer end of thecylinder. A radially outer or driver part of the piston 33 is reduced indiameter to receive a driving ring 35 suitably pinned to the wall of thecylinder and to the piston to permit axial movement between the cylinderbarrel and the piston and to rotatably drive the cylinder barrel 20along with the piston ring.

Two sets of leaf springs 36, each of which consist of a plurality ofleaves, extend across the bore of the end cylinder 32 from oppositesides of the shaft and have their end portions arranged into slots whichare formed diametrically opposite each other in the siidewall of thebore. The intermediate ends of the leaf springs 36 are slidable againstan abutment reaction membpr secured to the shaft. The springs, by actingupon the abutments and reaction abutment member, urge the cylinderbarrel in a direction off the taper of the pintle, and as shown in FIG.1 th cylinder barrel is in the center of its travel.

Since the bearing surfaces of the pintle part 10 and of the bushing 21in the cylinder barrel are tapered, the running clearance therebetweenis increased by moving the cylinder barrel 20 toward the right anddecreased by moving it toward the left. At the limit of its movementtoward the right, the running clearance between the pintle and cylinderbarrel is just sufficient to permit a relatively low pressure to causemotive liqfuid to form a lubricating film between the cylinder barreland the pintle.

The high pressure one of the ports l1, 12 in the pintle supplies fluidto the running clearance between the bearing surfaces of the pintle andthe cylinder barrel, and this leakage fluid escapes from both ends ofthe cylinder barrel. The pressure of the leakage fluid in the runningclearance between the cylinder barrel and pintle acts to urge thecylinder barrel in direction off the taper of the pintle. Leakage fluidescaping past the front end of the pintle and entering the end cylinder32 creates a pressure therein which acts upon the end face of thecylinder barrel to urge the cylinder barrel in a direction toward theleft in FIG. 1, and on the taper of the pintle. I

Leakage fluid is conducted from end cylinder 32 through a small passages37, 38, the latter extends axially through the pintle from one end tothe other end thereof and in turn is connected to a passage 43 in aschematically illustrated valve block 39 mounted on the rear end of thepintle and the hub 3 of the casing. The associated passage 43 in thevalve block is in turn connected, as hereinafter described, to a passage48 through the casing 1 so thaat the fluid escaping therethrough mayreturn through a drain passage from the casing to reservoir, not shown.The flow .of liquid through the passage 43 in the valve block is limitedby a suitable choke, such as an orifice 44, inserted in that passagedownstream of valve 50, so that pressure which may be created in the endcylinderr 32 is sufficient to move the cylinder barrel to a position onthe pintle. Thee escape of liquid from the end cylinder is resisted bythe choke 44, and therefore results in an increase of pressure in theend cylinder. The pressure of liquid in the end cylinder continues torise until it is high enough to overcome the resistance of the biasforces provided by hydraulic pressure acting between the pintle andcylinder, and by the force of the springs 36, then the pressure in theend cylinder 32 will move the cylinder barrel toward the large end ofthe pintle to reduce the running clearance between the cylinder barreland the pintle, and reduce the flow of leakage through it to the endcylinder at a point where the pressure in the end cylinder can bemaintained by the rate of flow through the orifice 44.

According to the present invention however, leakage fluid supplied bythe high pressure pintle port and flowing between the bearing surfacesof the pintle and cylinder barrel outwardly toward the large end of thepintle is collected in an annular groove 40 formed in the periphery ofthe pintle adjacent to the large end of its bearing surface. Thecollection groove 40 is connected by a radially drilled passage 41 tointerconnect with an axially drilled passage 42 extending to the end ofthe pintle for connection to a passage 45 in the valve block at thelarge end of the pintle. This passage is also, in turn, connected todrain passage 47 and end drain passage 48 to the interior of the casingthrough a flow restriction orifice 46 inserted in this passage 45downstream of valve 50 and it has substantially the same choke or flowrestricting properties as provided by the orifice 44 for leakage fluidescaping from the other end of the pintle.

The valve block 39 contains a servovalve 50, comprising a valve chambper51 one end of which is connected to the passage 43 receiving fluidescaping from the end cylinder at the small end of the pintle and theother end is connected to the passage 45 receiving fuid escaping throughthe collection groove 40 at the large end of the pintle bearing surface.A drain opening 53 serving as an additional drain opening from saidchamber is located intermediate said end passages and is normallyblocked by a movable valve member 52 in said valve chamber. The valvemember 52 may be moved entirely by hydraulic forces or also may bebiased by a light spring 54 in a direction to normally block the drainopening 53 and to prevent hunting of the valve. One end of theservovalve is onnected to the passages 43, 38, conducing leakage fluidfrom the end cylinder 32 at the small end of the pintle an the other endof the servovalve is connected to the passages 45, 42 conducting leakagefluid from the collection groove 40 at the large end of the pintle. Theservovalve 50 is connected ahead or upstream of the orifices 44, 46 sothat the pressure developed at the orifices appears in the servovalveto-react on opposite ends of the valve member.

The servovalve 50 is constructed and arranged so that the movable valvemember 52 is normally in the position shown, when the opposing pressuresacting on the valve member are equal or when the pressure of the leakagefluid from the large end of the pintle is greater. in that event, theservovalve is inoperative and the servomotor comprising end cylinder 32is the controlling factor as regulated by the rate of flow of fluiddischarging through its associated orifice 44. When, for any reason,however, the leakage flow from the large end of the pintle develops lesspressure at its dicharge orifice 46 than is developed at the dischargeorifice 44 by the leakage fluid from the small end of the pintle thenthe differential pressure acting on the servovalve displaces its movablevalve membper 52 to open the orifice port 53 and drain additional fluidfrom the end cylinder 32 through passage 55 until such pressures at thedischarge orifices at opposite ends of the cylinder equalize. The drainopening 53 in the valve member being gradually uncovered by the movablevalve member provides a variable opening and responds to a differentialpressure to operatively connect the drain opening in parallel with thefixed orifice 44 draining fluid from the end cylinder 32. When theeffective running clearance between the large end of the pintle and thecylinder barrel is in fact less than the effective running clearancefrom the smaller end of the pintle and the cylinder barrel, the flow ofleakage fluid from the large end of the pintle will be less than theflow from the smaller end of the pintle and will generate less pressureat the orifice 46 discharging leakage fluid from the large end of thepintle. This will cause the servovalve to variably open the drainopening 53 to passage 55 to drain fluid from the end cylinder 32 andcause the cylinder barrel 20 to move off the taper to establish agreater overall running clearance until the differential pressure on theservovalve is minimized. Variable opening 53 is shown connected througha fixed orifice 49 to drain passages 47, 48.

The pressure in end cylinder 32 is positively limited 7 by a reliefvalve 56 located in the valve block 39 and relief valve 56 operativelyconnects passage 43 to drain passages 47, 48.

Although it is preferred to use a fixed orifice 44 operatively connectedin parallel with a variable opening 53, it is understood that a singlevariable opening is equivalent thereto when arranged for a predeterminedminimum opening serving both as a fixed orifice and a variable orifice.

I claim:

1. A hydraulic pump or motor having a cylinder barrel journalled on atapered pintle with the axial position of the cylinder barrel varied tomaintain a necessary running clearance between the bearing surfacesdefined by their mating tapered surfaces, leakage fluid supplied fromoperating ports in the cylinder barrel and pintle escaping from betweentheir running clearance to opposite ends thereof, a servo-motorresponsive to the pressure of leakage fluid escaping at one end of saidpintle urges said cylinder barrel in a direction to reduce the runningclearance, and a servovalve responsive to thee differences in thepressures of the leakage fluid escaping at both ends of said pintle isoperative to bleed fluid from said servomotor when the pressure ofleakage fluid therein from said one end is greater than the pressure ofleakage fluid escaping from the other end of said pintle.

2. A hydraulic pump or motor having a cylinder barrel with a taperedbore journalled on a tapered pintle and the mating surfaces thereofdefining tappered bearing surfaces, inlet and outlet ports in saidpintle to con duct fluid between cylinders and said cylinder barrel andpassages in said pintle and also to supply leakage fluid along therunning clearance between the tapered bearing surfaces, a servomotor toreceive leakage fluid discharging from said bearing surfaces at one endof said pintle and position said cylinder barrel on said servomotor foreffecting a predetermined minimum flow of leakage fluid between saidbearing surfaces at one end of said pintle, said pump or motorcharacterized by means for effecting a predetermined minimum flow ofleakage fluid between said bearing surfaces at the other end of saidpintle, said means comprising a servovalve having a discharge openingand a valve member interrupting said opening, opposite ends of saidservovalve connected respectively to receive leakage fluid from oppositeends of said pintle valve and operable to conduct leakage fluid fromsaid one end of said pintle to said discharge opening when the pressurethereof on said valve member exceeds its opposing pressure.

3. In a hydraulic pump or motor having a cylinder barrel journalled forrotation on a tapered pintle, inlet and outlet ports in the pintleintermediate the ends of the bearing surface of the pintle, leakagefluid supplied from said ports to flow between the bearing surfaces andescape at both ends thereof, a servomotor comprising a cylinder arrangedat one end of the cylinder barrel to receive leakage fluid escaping fromsaid one end and connected to a first orifice for discharging saidleakage fluid at a limited rate, passage means collecting leakage fluidflowing between the bearing surfaces and escaping at the other end and asecond orifice discharging such leakage fluid at a limited rate, and avalve having ports connected ahead of said first and second orifices toreceive leakage fluid from both ends of said bearing surfaces, saidvalve having a movable valve member between the ports thereof and adischarge opening closed by said valve member when the pressure at saidsecond orifice is equal to or greater than the pressure at said firstorifice, and said discharge opening being variably opened to leakagefluid at said first orifice when the pressure thereof is greater thanthe pressure of leakage fluid at said second orifice, whereby thepressure of the leakage fluid in said cylinder of said servomotorpositions said cylinder barrel on said pintle to maintain at least apredetermined minimum flow of leakage fluid to both ends of said bearingsurfaces.

4. In a pump or motor as described in claim 3 in which said one end ofsaid bearing surfaces is at the small end of the pintle and the otherend is at the large end of the pintle, and the servomotor is arranged atthe small end of the pintle.

S. In a pump or motor as described in claim 3 in which said servomotoris arranged at the small end of the pintle to receive leakage fluidescaping from between the bearing surfaces at that end, a valve blockmounted on the other end of said pintle and containing said orifices andsaid valve, a first passage extending axially through said pintle to thecylinder of said servomotor and connected to one port in said valve andsaid first orifice, a second passage in said pintle connected to asecond port in said valve and said second orifice, an annular groove inthe periphery of the bearing surface of the pintle adjacent the largeend thereof and connected to said second passage in said pintle toconduct leakage fluid escaping from between the bearing surfaces at thelarge end of the pintle to said second port in said valve and to saidsecond orifice.

1. A hydraulic pump or motor having a cylinder barrel journalled on atapered pintle with the axial position of the cylinder barrel varied tomaintain a necessary running clearance between the bearing surfacesdefined by their mating tapered surfaces, leakage fluid supplied fromoperating ports in the cylinder barrel and pintle escaping from betweentheir running clearance to opposite ends thereof, a servo-motorresponsive to the pressure of leakage fluid escaping at one end of saidpintle urges said cylinder barrel in a direction to reduce the runningclearance, and a servovalve responsive to thee differences in thepressures of the leakage fluid escaping at both ends of said pintle isoperative to bleed fluid from said servomotor when the pressure ofleakage fluid therein from said one end is greater than the pressure ofleakage fluid escaping from the other end of said pintle.
 2. A hydraulicpump or motor having a cylinder barrel with a tapered bore journalled ona tapered pintle and the mating surfaces thereof defining tapperedbearing surfaces, inlet and outlet ports in said pintle to conduct fluidbetween cylinders and said cylinder barrel and passages in said pintleand also to supply leakage fluid along the running clearance between thetapered bearing surfaces, a servomotor to receive leakage fluiddischarging from said bearing surfaces at one end of said pintle andposition said cylinder barrel on said servomotor for effecting apredetermined minimum flow of leakage fluid between said bearingsurfaces at one end of said pintle, said pump or motor characterized bymeans for effecting a predetermined minimum flow of leakage fluidbetween said bearing surfaces at the other end of said pintle, saidmeans comprising a servovalve having a discharge opening and a valvemember interrupting said opening, opposite ends of said servovalveconnected respectively to receive leakage fluid from opposite ends ofsaid pintle valve and operable to conduct leakage fluid from said oneend of said pintle to said discharge opening when the pressure thereofon said valve member exceeds its opposing pressure.
 3. In a hydraulicpump or motor having a cylinder barrel journalled for rotation on atapered pintle, inlet and outlet ports in the pintle intermediate theends of the bearing surface of the pintle, leakage fluid supplied fromsaid ports to flow between the bearing surfaces and escape at both endsthereof, a servomotor comprising a cylinder arranged at one end of thecylinder barrel to receive leakage fluid escaping from said one end andconnected to a first orifice for discharging said leakage fluid at alimited rate, passage means collecting leakage fluid flowing between thebearing surfaces and escaping at the other end and a second orificedischarging such leakage fluid at a limited rate, and a valve havingports connected ahead of said first and second orifices to receiveleakage fluid from both ends of said bearing surfaces, said valve havinga movable valve member between the ports thereof and a discharge openingclosed by said valve member when the pressure at said second orifice isequal to or greater than the pressure at said first orifice, and saiddischarge opening being variably opened to leakage fluid at said firstorifice when the pressure thereof is greater than the pressure ofleakage fluid at said second orifice, whereby the pressure of theleakage fluid in said cylinder of said servomotor positions saidcylinder barrel on said pintle to maintain at least a predeterminedminimum flow of leakage fluid to both ends of said bearing surfaces. 4.In a pump or motor as described in claim 3 in which said one end of saidbearing surfaces is at the small end of the pintle and the other end isat the large end of the pintle, and The servomotor is arranged at thesmall end of the pintle.
 5. In a pump or motor as described in claim 3in which said servomotor is arranged at the small end of the pintle toreceive leakage fluid escaping from between the bearing surfaces at thatend, a valve block mounted on the other end of said pintle andcontaining said orifices and said valve, a first passage extendingaxially through said pintle to the cylinder of said servomotor andconnected to one port in said valve and said first orifice, a secondpassage in said pintle connected to a second port in said valve and saidsecond orifice, an annular groove in the periphery of the bearingsurface of the pintle adjacent the large end thereof and connected tosaid second passage in said pintle to conduct leakage fluid escapingfrom between the bearing surfaces at the large end of the pintle to saidsecond port in said valve and to said second orifice.